Development of nutritious rice with high zinc/selenium and low cadmium in grains through QTL pyramiding

Abstract

Enriching zinc (Zn) and selenium (Se) levels, while reducing cadmium (Cd) concentration in rice grains is of great benefit for human diet and health. Large natural variations in grain Zn, Se, and Cd concentrations in different rice accessions enable Zn/Se‐biofortification and Cd‐minimization through molecular breeding. Here, we report the development of new elite varieties by pyramiding major quantitative trait loci (QTLs) that significantly contribute to high Zn/Se and low Cd accumulation in grains. A chromosome segment substitution line CSSLGCC7 with the PA64s‐derived GCC7 allele in the 93‐11 background, exhibited steadily higher Mn and lower Cd concentrations in grains than those of 93‐11. This elite chromosome segment substitution line (CSSL) was used as the core breeding material to cross with CSSLs harboring other major QTLs for essential mineral elements, especially CSSLGZC6 for grain Zn concentration and CSSLGSC5 for grain Se concentration. The CSSLGCC7+GZC6 and CSSLGCC7+GSC5 exhibited lower Cd concentration with higher Zn and Se concentrations in grains, respectively. Our study thus provides elite materials for rice breeding targeting high Zn/Se and low Cd concentrations in grains.

Breeding and biotechnological interventions for trait improvement: status and prospects

“…Reference genome, together with the resequencing data of all available accessions of a given species, have the considerable potential to expedite molecular breeding as it deploys the entire genetic diversity existing in the species. Development of pangenomes for crop species has been carried out in several plants, such as rice (Schatz et al 2014 ; Zhao et al 2018 ; Zhou et al 2020 ), maize (Hirsch et al 2014 ; Xu et al 2014 ), soybean (Lam et al 2010 ; Li et al 2014 ; Liu et al 2020a , b ) and Brassica (Golicz et al 2016a ; Bayer et al 2019 ). The quality of the reference assembly determines the appliance of plant pangenomics in terms of size, completeness and annotation, selection, and dense phenotyping of appropriate genotypes (Golicz et al 2016b ).…”

Strategies to manage the risk of heavy metal(loid) contamination in agricultural soils

“…For example, by introgressing qCd7 from the japonica cultivar Nipponbare containing a strong allele of OsHMA3 to indica rice hybrids, grain Cd concentration was reduced by about 50% [46] . QTLs for low Cd and for high selenium (Se) or Zn in grain, beneficial to human nutrition, can be introduced into elite rice cultivars through QTL pyramiding and marker-assisted molecular breeding [47] . Allelic variation in BrHMA3 also has an important role in Cd accumulation in the leaves of Brassica rapa vegetables; strong alleles of BrHMA3 can be used to breed low Cd Brassica vegetables [48] .…”

QTL pyramiding for producing nutritious and safe rice grains

“…In a study in the current issue of JIPB, Liu et al (2020) developed elite rice lines simultaneously with low Cd and high Zn or Se accumulation in grains by QTL pyramiding. By using the recombinant inbred lines (RILs) derived from a crossing between 93‐11 and PA64s (Zhang et al 2019a), the two varieties that were used to develop the widely grown pioneer super hybrid rice Liang‐You‐Pei‐Jiu (LYPJ) in China, several grain elemental QTLs were identified, including three grain Zn QTLs and two grain Se QTLs (Liu et al 2020). Among these QTLs, the grain Zn QTL GZC6 on chromosome 6 and the grain Se QTL GSC5 on chromosome 5, which explained 16.4% and 13.8% of phenotypic variation respectively, were chosen for QTL pyramiding.…”

“…Two pyramiding lines CSSL GCC7+GZC6 and CSSL GCC7+GSC5 were generated by marker assisted selection. The figure was modified from Liu et al (2020).…”

“…The study by Liu et al (2020) presents a successful example in the development of rice materials enriched with essential mineral nutrient and reduced toxic elements in grains by QTL pyramiding. However, further improvements are needed because the grain Cd concentrations in the pyramiding lines, although reduced significantly, still exceeded the Chinese maximum permissible limit when grown in Cd contaminated soils.…”